Nonlinear finite element analyses of prestressed concrete beams strengthened with CFRP laminate

Nonlinear finite-element (FE)-based quasi-static and vibration analyses of prestressed concrete beams with carbon fiber-reinforced polymer (CFRP) laminate are conducted. To establish nonlinearities in concrete and prestressing steel material properties and concrete-steel interfaces in FE modeling, numerical models of reinforced concrete (RC) and prestressed concrete (PSC) beams are developed, and their response is assessed with experimental results. The established FE model is then extended so as accurately to model CFRP laminate and the nonlinear interaction at concrete-CFRP interfaces between RC and PSC beams. Cohesive interface elements capable of showing delamination failure are introduced to model the adhesion between a concrete beam and the CFRP laminate at its soffit. Ignoring such interaction overestimates the load-carrying capacity of the beam apart from its inability to capture the delamination. The effect of the prestressing force, location and profile of prestressing tendons on the modal frequencies of unstrengthened and CFRP-strengthened beams is studied. Strengthened beams have higher fundamental frequencies, and their modal frequencies are independent of prestressing force, varying significantly with the location and profile of tendons.